It sounds nice, but I don't think this would get very far... It's just not a very smooth concept and it would bring nasty disadvantages with it too... ;/
could you elaborate? why not very smooth? what disadvantages? it seems like two coins already up and running on this concept.
One of the issues is that these DAG-based approaches give away the benefit of making "blocks" and merkle trees. This means that the ledger side rises linearly with tx count..there is no way to "prune" it..whereas in blockchain you could just store the headers and have merkle proofs to verify block membership.
Other issue is that the resulting structure is unwieldy and exposes lots of additional attack surfaces. Blockchain on the other hand is ideally a single linear chain or in the worst case some orphan blocks and a few forks..which makes it easier to analyze.